A chemical messenger secreted by an endocrine gland and carried in the blood.

What is a target cell?

A cell with receptors that are complementary to a particular hormone.

Why does a hormone only affect target cells?

Only target cells have the receptors with a shape that is complementary to the hormone.

Why can adrenaline not enter a cell?

It is not lipid-soluble, so it cannot cross the phospholipid bilayer.

Which enzyme makes cAMP?

Adenylyl cyclase, which converts ATP to cAMP.

What does the adrenaline response in the liver produce?

Glycogen is broken down to glucose, which is released into the blood.

How does a second messenger amplify the response?

Each activated enzyme activates many more, so a small amount of hormone causes a large response.

How does oestrogen enter a cell?

It is lipid-soluble, so it diffuses through the phospholipid bilayer.

How does the oestrogen-receptor complex act?

As a transcription factor: it binds to DNA and stimulates transcription of specific genes.

Why is the oestrogen response slower than the adrenaline response?

New proteins must be made, whereas adrenaline activates enzymes already in the cell.

Chemical control in mammalsEdexcel A-Level Biology B: Flashcards

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What is an endocrine gland?

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What is an endocrine gland?: A ductless gland that secretes hormones directly into the blood.
What is a hormone?: A chemical messenger secreted by an endocrine gland and carried in the blood.
What is a target cell?: A cell with receptors that are complementary to a particular hormone.
Why does a hormone only affect target cells?: Only target cells have the receptors with a shape that is complementary to the hormone.
Why can adrenaline not enter a cell?: It is not lipid-soluble, so it cannot cross the phospholipid bilayer.
What is the first messenger in the adrenaline response?: Adrenaline.
What is the second messenger in the adrenaline response?: cAMP (cyclic AMP).
Which enzyme makes cAMP?: Adenylyl cyclase, which converts ATP to cAMP.
What does the adrenaline response in the liver produce?: Glycogen is broken down to glucose, which is released into the blood.
How does a second messenger amplify the response?: Each activated enzyme activates many more, so a small amount of hormone causes a large response.
How does oestrogen enter a cell?: It is lipid-soluble, so it diffuses through the phospholipid bilayer.
How does the oestrogen-receptor complex act?: As a transcription factor: it binds to DNA and stimulates transcription of specific genes.
Why is the oestrogen response slower than the adrenaline response?: New proteins must be made, whereas adrenaline activates enzymes already in the cell.

Exam questions on Chemical control in mammals

The adrenal glands, the thyroid gland and the pancreas are endocrine glands. A hormone released from an adrenal gland is carried in the blood to every tissue in the body, but only some tissues respond to it.
Explain why adrenaline causes a response in liver cells but not in every cell it reaches.2 marks
Adrenaline is secreted by the adrenal glands during a stress response. In a liver cell, adrenaline binds to a receptor on the cell surface membrane. This activates an enzyme, adenylyl cyclase, which converts ATP to cyclic AMP (cAMP). The cAMP then activates other enzymes in the cell, which break down glycogen to glucose.
Explain how the use of a second messenger allows a small amount of adrenaline to cause a large response.2 marks
Oestrogen is a steroid hormone secreted by the ovaries. It is lipid-soluble. It stimulates cells in the lining of the uterus to grow and to produce new proteins.
Describe how oestrogen causes a target cell to produce a new protein.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).